Method and apparatus for drying paint



. Dem 1941- H. A. TOULMIN,. JR 2,267,001

METHOD AND APRARATUS FOR DRYING PAINT I F iled Dec. 16, 1940 swan u munmum HARRY RTOUUMN JR.

ILCTRIIL ATTORNEYS Patented Dec. 23, 1941 METHOD AND APPARATUS FORDRYING PAINT Harry A. Toulmin, Jr., Dayton, Ohio, assignor to TheCommonwealth Engineering Company, Dayton, Ohio, a corporation of OhioApplication December 16, 1940, Serial No. 370,297

4 Claims.

My invention relates to a method of drying films, and more particularlyto a novel apparatus and method of baking or drying enamel, lacquer andsimilar coatings in the finishing of articles.

It is a principal object of this invention to devise a method ofinduction heating of metal surfaces so as to rapidly dry a coating filmapplied thereover.

Another object of this invention is to provide a novel induction heatingdevice which is applicable as a hand tool for applying to a paintedsurface so as to heat the base metal on which the coating has beenapplied to effect the drying of the coating.

Another object is to heat electrically conducting articles, such ascastings, pressed steel, aluminum and like metal articles which havebeen coated with a liquid coating composition, by electrical inductionfrom a high frequency current in order to bake or dry the coating.Another object is to provide a portable induction heating apparatuswhich can be moved over the surface of an article to heat the metal baseby induced electrical current with or without moving the article beingtreated.

Another object is to provide an apparatus and method for continuouslyfinishing articles which have been coatedand whereby the article isheated by electrical induction from a high frequency alternatingelectric current so as to bring about drying of the film to produce afinishedv article.

These and other objects and advantages will appear from the followingdescription taken in connection with the drawing, wherein Figure l is .aperspective view illustrating the use of my induction heating apparatusfor heating a freshly painted article, such as the tailstock of a lathemachine;

Figure 2 is an elevational view of a modified apparatus used as asupplement to my hand operated induction heating device asemployed fordrying large machine elements or frame parts wherein it is desired toutilize means for sup-.

and illustrating its application to a coated metal surface; I

ished which are suitably conveyed along on an endless conveyor;

I Figure 5 is a view taken substantially on the line 5-5 of Figure 4 andlooking in the direction of the arrows.

In general, it has been the practice heretofore to accelerate the dryingof paint and lacquer coatings as applied to articles by placing the samein an oven or the like means whereby the coating can be subjected toheat treatment. This method necessitates the provision of various sizedovens and heat exchanging means in order to handle coated articles whichare to be dride or upon which the finish is to be baked. My inventioneliminates the need for this equipment and expensive apparatus andprovides a novel means and method for drying the coating applied on anarticle by merely placing a device comprising a primary induction coilcarrying high frequency current in close proximity to the coated metalsurface whereby to induce sufflcient amount of electric current to flowthrough the metal adjacent the coating to heat the metal drying thecoating.

My invention is particularly useful in finishing large pieces ofmachinery, such as castings, machine frames and irregular shapedarticles which require a very large capacity oven and are otherwisedifficult to heat so as to dry or bake the coating to produce a finishedproduct.

In one embodiment of my invention a manually manipulated inductionheating device is provided comprising a primary coil which is fluidcooled and is arranged to be moved over the surface of the article to beheat treated. I prefer that the heating is effected through the use ofhigh frequency alternating currents, as the heating is much moreeffective when high frequency currents are used. The heating effect willbe better in a magnetizable article than in one which is merelyconductive, but my method and apparatus are applicable for heating bothtypes of articles.

Referring to the drawing in detail, in Figure 1 there is illustrated atailstock casting piece 10, the surface of which is locally heated bymoving the induction coil in the heating device, generally designatedl2, back and forth in close proximity Figure 4 is an elevational view,partly in section, of a modified apparatus for continuous into thesurface of the article, as indicated by the arrows. The primaryinduction heating coil device I2. is manually grasped and moved over thesurface of the article similarly as in spraying the casting with acoating composition, the heating being effected by the induced eddycurrents,

duction heat treating of the articles being-fin- 55 and with an ironbase both hysteresis and eddy currents will be set up within the metalwhen high frequency electric current is flowing through the primary coilof the device 92.

The detailed construction of my manual induction tool device isillustrated in Figure 3 wherein an integral casing 35 encloses theprimary coil ill in the chamber i8 which is arranged to be cooled by thecirculation of water or' other cooling fluid through the conduit intothe chamher it in contact with the coil and outward through theconcentric passageway 22 in the conduit member 25. lhe casing 55 ispreferably made of electrical and heat insulating material and thehandle 25 for grasping the induction device may be made integral withthe casing, as illustrated in Figure 3. Electric current is supplied tothe coil if by means of the electrical conduit means 26. As shown, themetal surface portion 2'11 of the article having the coating 29' isdried by the induced electrical current set up in the metal portion 27when the induction coil device is held in close proximity to the coatedsurface, as illustrated in Figure 3.

Where the magnetism of the article is sumclent to make it impractical tomanually hold the primary coil heating device i2 a proper distance fromthe work, a supplemental supporting frame means 30 may be provided forholding the induction coil device 52 a proper distance from the surfaceof the work to be heat treated. This supplemental supporting member 39may comprise a rectangular frame having a cross bar 32 mounted forvertical reciprocation in the side channel members- 36 by means of therollers 35. The induction heating coil device 32 is slidably supportedon the transverse rod 32 and is arranged whereby the operator can graspthe handle 25 and move the induction heating coil device 82 verticallyand laterally, as required, to heat the surface of the article andeffect drying of the coating. Preferably the supporting frame means 30is mounted on a portable base means 37 so that the device can be'movedfrom one article to another and suitably positioned adjacent the work.

The use of high frequency current, on the order of 10,000 to 50,000cycles, is contemplated. Passage of high frequency current of lowvoltage and high amperage through the induction coil while the device isheld close to but not actually touching the surface of the coatedarticle induces a current in the surface of the metal which rapidlybakes the coating applied over the surface.

As illustrated in Figure 2, the article. being treated, such'as shown at39, is mounted on a rotatable base 30.

article at a predetermined distance is readily effected.

In the arrangement shown in Figures 4 and 5 provision is made wherebythe articles being finished can be supported on an endless conveyor andmoved between inductors shaped to conform generally with the articlebeing finished. This construction is adapted for production drying ofcoated articles. As illustrated, the article is suitably supported on anoverhead trackway means, generally designated 41, and the primaryinduction coil members 49 and 50 are positioned around the article so asto conform generally with its surface contour. The primary inductioncoil members are supported on the overhead structural member 52bybracket means 54, and are connected to a source of high frequency Inthis way, the application of the drying device to the surface of thecoated electric current by the wires 51;. When current is supplied tothe primary coils the metal surface of the coated article is heated bythe induced eddy currents to bring about drying of the film. Themovement of the coated articles between the induction coils Q9 and 50 ispreferably intermittent but with the use of multiple coils theprocessing of the articles may be continuous.

Where the coated'article to be dried comprises a nonmetallic base, theinduction heat drying may be effected by mounting or encasing thearticle within an electrically conducting material in which the inducedelectric current can be made to indirectly heat the coating and effectdrying of the same to a hard tough film.

Further, as a modification of the fluid cooled primary coil means ll,there may be employed coils of pipe so as to form a water coolingsystem. The pipe, in this instance, forms the primary coil through whichcooling water is flowed to maintain the coil at the proper temperature.In order to prevent leakage of current it is only necessary to insert asection ofinsulating pipe in the discharge line, since the conductivityof ordinary water to high frequency current is low enough to besubstantially negligible. Variations in the shape of the device may bemade in order that the maximum effect of the induced current for heatingthe article can be set up and the de sired uniformity of heatingsecured.

Moreover, I do not limit my invention to the use of single-phaseelectrid current, but where desired multiphase high frequency currentobtained from any multiphase source may be utilized. Likewise, one ormore coils may be used in place of one primary coil. It will be observedthat my method and mechanism are capable of use generally to heat alocalized surface of an article and that either the article may be movedor the primary induction coil device or both. Further, the inductionheating of coated articles may be applied to special forms or objects byshaping the coils to conform to the contour of the article, as required,to subject the same to high frequency induced electric current.

It will be also understood that my apparatus and the application of myprocess may be greatly varied without departing from the spirit andscope of my invention and that such modifications will be readilyunderstood by those skilled in the art and may be made to adapt thisinvention to various conditions and uses.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. A method of baking industrial finishes on electrical conductingsurfaces of irregular contour including the steps of (a) focusing asource of inductive heat from a high frequency current on a limited areaof the object to be treated, (b) adjusting the distance of heat sourcefrom the object, and (c) regulating the time of application of the heatto the area under baking treatment and the rate of movement of bakingheat on the object, and (d) the relative angular position of theinduction coil of the source of heat to the object, in accordance withthe thickness of the industrial finish on the object.

2. A method of baking industrial finishes on electrical conductingsurfaces of irregular contour including the steps of (a) focusing asource of inductive heat from a high frequency current on a limited areaof the object to be treated, (b) adjusting the distance of heat sourcefrom the object, (o) regulating the time of application of the heat tothe area under baking treatment and the rate of movement of baking heaton the object, and (d) the relative angular position of the inductioncoil of the source of heat to the object, in accordance with thethickness of the industrial finish on the object, and (e) simultaneouslycooling said source of heat.

3. As an article of manufacture, in combination a manually movableinduction heating device for' heat treating articles, and meanscomprising a portable supporting member including a vertical standhaving a track for holding said device a predetermined distance from thearticle to be heated, said device having means engaging said track forvertical movement thereon, and handle means on said induction heatingdevice whereby said heating device and stand may be moved aroundarticles of different shapes and sizes, and whereby said heating devicemay be moved on said track, or held in adjusted position thereon.

4. As an article of manufacture, a heating device for drying coatedmetal articles comprising a casing, an induction coil mounted in saidcasing, and means for conducting high frequency current of low voltageand high amperage through said induction coil, said device having ahandle and means for movably mounting said device on a portable standwhereby said casing and its coil may be moved around irregularly shapedobjects, and is adapted to be positioned in close proximity to saidcoated metal objects without touching the surface whereby an electriccurrent is induced in the surface of the metal which rapidly dries thecoating film thereon.

HARRY A. TOULMIN, JR

